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Background and Purpose: Remote ischaemic preconditioning (rIPC) for cardioprotection is severely impaired in diabetes, and therapeutic options to restore it are lacking. The vascular endothelium plays a key role in rIPC. Given that the activity of endothelial nitric oxide synthase (eNOS) is inhibited by proline‐rich tyrosine kinase 2 (Pyk2), we hypothesized that pharmacological Pyk2 inhibition could restore eNOS activity and thus restore remote cardioprotection in diabetes. Experimental Approach: New Zealand obese (NZO) mice that demonstrated key features of diabetes were studied. The consequence of Pyk2 inhibition on endothelial function, rIPC and infarct size after myocardial infarction were evaluated. The impact of plasma from mice and humans with or without diabetes was assessed in isolated buffer perfused murine hearts and aortic rings. Key Results: Plasma from nondiabetic mice and humans, both subjected to rIPC, caused remote tissue protection. Similar to diabetic humans, NZO mice demonstrated endothelial dysfunction. NZO mice had reduced circulating nitrite levels, elevated arterial blood pressure and a larger infarct size after ischaemia and reperfusion than BL6 mice. Pyk2 increased the phosphorylation of eNOS at its inhibitory site (Tyr656), limiting its activity in diabetes. The cardioprotective effects of rIPC were abolished in diabetic NZO mice. Pharmacological Pyk2 inhibition restored endothelial function and rescued cardioprotective effects of rIPC. Conclusion and Implications: Endothelial function and remote tissue protection are impaired in diabetes. Pyk2 is a novel target for treating endothelial dysfunction and restoring cardioprotection through rIPC in diabetes. [ABSTRACT FROM AUTHOR]

Cellular heterogeneity is a well-accepted feature of tissues, and both transcriptional and metabolic diversity have been revealed by numerous approaches, including optical imaging. However, the high magnification objective lenses needed for high-resolution imaging provides information from only small layers of tissue, which can result in poor cell statistics. There is therefore an unmet need for an imaging modality that can provide detailed molecular and cellular insight within intact tissue samples in 3D. Using GFP-tagged GLUT4 as proof of concept, we present here a novel optical mesoscopy approach that allows precise measurement of the spatial location of GLUT4 within specific anatomical structures across the myocardium in ultrathick sections (5 mm x 5 mm x 3 mm) of intactmouse heart.We reveal distinct GLUT4 distribution patterns across cardiac walls and highlight specific changes in GLUT4 expression levels in response to high fat dietfeeding, and we identify sex-dependent differences in expression patterns. This method is applicable to any target that can be labelled for light microscopy, and to other complex tissues when organ structure needs to be considered simultaneously with cellular detail. [ABSTRACT FROM AUTHOR]

Aims: Exercise training induces white adipose tissue (WAT) beiging and improves glucose homeostasis and mitochondrial function in rodents. This could be relevant for type 2 diabetes in humans, but the effect of physical fitness on beiging of subcutaneous WAT (scWAT) remains unclear. This translational study investigates if beiging of scWAT associates with physical fitness in healthy humans and recent‐onset type 2 diabetes and if a voluntary running wheel intervention is sufficient to induce beiging in mice. Materials and Methods: Gene expression levels of established beiging markers were measured in scWAT biopsies of humans with (n = 28) or without type 2 diabetes (n = 28), stratified by spiroergometry into low (L‐FIT; n = 14 each) and high physical fitness (H‐FIT; n = 14 each). High‐fat diet‐fed FVB/N mice underwent voluntary wheel running, treadmill training or no training (n = 8 each group). Following the training intervention, mitochondrial respiration and content of scWAT were assessed by high‐resolution respirometry and citrate synthase activity, respectively. Results: Secreted CD137 antigen (Tnfrsf9/Cd137) expression was three‐fold higher in glucose‐tolerant H‐FIT than in L‐FIT, but not different between H‐FIT and L‐FIT with type 2 diabetes. In mice, both training modalities increased Cd137 expression and enhanced mitochondrial content without changing respiration in scWAT. Treadmill but not voluntary wheel running led to improved whole‐body insulin sensitivity. Conclusions: Higher physical fitness and different exercise interventions associated with higher gene expression levels of the beiging marker CD137 in healthy humans and mice on a high‐fat diet. Humans with recent‐onset type 2 diabetes show an impaired adipose tissue‐specific response to physical activity. [ABSTRACT FROM AUTHOR]

Insulin-stimulated muscle glucose uptake is a key process in glycemic control. This process depends on the redistribution of glucose transporters to the surface membrane, a process that involves regulatory proteins such as TBC1D1 and TBC1D4. Accordingly, a TBC1D4 loss-of-function mutation in human skeletal muscle is associated with an increased risk of type 2 diabetes, and observations from carriers of a TBC1D1 variant associate this protein to a severe obesity phenotype. Here, we identified interactors of the endogenous TBC1D4 protein in human skeletal muscle by an unbiased proteomics approach. We detected 76 proteins as candidate TBC1D4 interactors. The binding of 12 of these interactors was regulated by insulin, including proteins known to be involved in glucose metabolism (e.g., 14-3-3 proteins and α-actinin-4 [ACTN4]). TBC1D1 also coprecipitated with TBC1D4 and vice versa in both human and mouse skeletal muscle. This interaction was not regulated by insulin or exercise in young, healthy, lean individuals. Similarly, the exercise- and insulin-regulated phosphorylation of the TBC1D1-TBC1D4 complex was intact. In contrast, we observed an altered interaction as well as compromised insulin-stimulated phosphoregulation of the TBC1D1-TBC1D4 complex in muscle of obese individuals with type 2 diabetes. Altogether, we provide a repository of TBC1D4 interactors in human and mouse skeletal muscle that serve as potential regulators of TBC1D4 function and, thus, insulin-stimulated glucose uptake in human skeletal muscle. [ABSTRACT FROM AUTHOR]